Hitherto, an optical element which can change a refractive power by changing a curvature of an interface between two types of liquids has been known.
FIG. 9A shows a refractive power variable element 100 making use of two types of liquids that do not mix with each other. A curvature of an interface between an electrolyte 103 and a non-electrolyte 104 can be changed by adjusting a contact angle of the liquids as a result of applying a voltage to electrodes 101 and 102 disposed at peripheral portions of the interface.
FIG. 9B shows a refractive power variable element 200 including a resilient film 203 between two types of liquids 201 and 202. A refractive power can be changed by deforming the resilient film 203 with driving means 204 such as an actuator. According to such a refractive power variable element 200, for the two types of liquids 201 and 202, liquids that tend to mix with each other may be selected.
A zoom lens making use of a refractive power variable element such as that described above is known. In zoom lenses in PTL 1 and PTL 2, a refractive power variable element is used to reduce the amount of movement of each lens unit when zooming, thereby reducing an overall lens length.